D5
“A Closed Game (or Double Queen's Pawn Opening) is a chess opening that begins with the moves: … The move 1.d4 offers the same benefits to development and center control as does 1.e4, but unlike with the King Pawn openings where the e4 pawn is undefended after the first move, the d4 pawn is protected by White's queen.”
https://chess.stackexchange.com/questions/6486/why-is-d5-the-best-move-in-this-position